The invention is directed to a shield having spring tongues which deflect inwardly in response to flow in the intake pipe of an internal combustion engine having spark ignition. Such a device is shown in German Offenlegungsschrift No. 26 41 066, the spring tongues of which are deflected from their radial position of rest by the flow medium in such a way that with rising flow medium pressure throughput the flow diameter of the apertured shield is automatically increased. This leads to a turbulence of the medium in the intake pipe, resulting in a good mixture preparation and favorable ignition conditions as well as a rapid flame propagation in the mixture compressing chamber of an internal combustion engine with external ignition. Experience shows that the improvement in combustion achieved with this shield often is not sufficient, especially in high-load internal combustion engines.